This invention relates to tire retreading operations of the type wherein, in preparation for treatment within a heated pressure chamber, a rim-mounted tire having a replacement tread strip thereon is partially enclosed by a flexible impervious envelope having marginal edge portions that overlie opposite sidewalls of the tire and that in turn are overlaid by respective ones of a pair of annular envelope-sealing members. The invention more specifically relates to an improved apparatus for positioning and securing the annular sealing members in axially-aligned relationship to the rim-mounted tire and in overlying relationship to opposite ones of the envelope margins and tire sidewalls.
Commonly-assigned U.S. Pat. No. 4,092,203 discloses a tire retreading apparatus of the general type described above and wherein a first one of the annular sealing members has a shaft that projects axially from its center hub through the tire-mounting rim and thence through and beyond an opening provided within the center hub of the second one of the annular sealing members. The end portion of the shaft projecting beyond the second sealing member has clamping means associated therewith and, depending upon the width dimensions of the particular tire disposed between the annular members, may have one or more spacer discs mounted thereon between the clamping means and the center hub of the second annular member. While the aforesaid apparatus possesses numerous beneficial features, it is also subject to certain deficiencies. One person cannot assemble the annular members upon opposite sides of the rim-mounted and envelope-enshrouded tire while it is in an upright position. Each assembly operation therefore requires two persons, or requires that the tire be laid upon its side. Secondly, and irrespective of which the foregoing assembly procedures is followed, there is no assurance that the same will result in the annular members being in precise axial alignment with the tire, as is desirable. Thirdly, the projection of the free end portion of the shaft carried by the first annular member outwardly beyond the hub of the second annular member increases the overall width of the completed assembly, and therefore lessens the number of similar assemblies that can be simultaneously treated within the heated pressure chamber. Lastly, the spacer discs employed in the aforesaid apparatus, for the purpose of permitting its accommodation of tires of varying widths, add to both its cost and assembly-time.